title: Antibody response to pneumococcal vaccination as a function of preimmunization titer.
abstract: BACKGROUND
  The interpretation of an adequate response to the unconjugated 23-valent pneumococcal vaccine for serotypes having high preimmunization titers remains challenging.
  
  
  OBJECTIVE
  We sought to determine whether high preimmunization titers preclude a 4-fold or greater response to vaccination. Moreover, we sought to determine the effect of the following covariates on this response: absolute preimmunization titer value, age, sex, serum IgG level, and serum IgG subclasses.
  
  
  METHODS
  We conducted a retrospective analysis of patients who were seen in our immune disorders clinic between 2001 and 2007 who had received the unconjugated 23-valent pneumococcal vaccine. Logistic regression was used to estimate the effect of different covariates, including preimmunization titer values, age, sex, IgG levels, and IgG subclass values, on the odds of a 4-fold or greater antibody response.
  
  
  RESULTS
  Per serotype, 10% to 40% of subjects with a high preimmunization titer attained at least a 4-fold response to vaccination. However, the odds of a 4-fold or greater response were found to decrease as a function of the absolute preimmunization titer value with an absolute value for each serotype beyond which the odds ratio approached zero.
  
  
  CONCLUSIONS
  High pneumococcal preimmunization titers do not necessarily preclude a 4-fold or greater response to vaccination. However, there appear to be serotype-specific preimmunization titer values, ranging from 4.4 to 10.3 microg/mL, above which a 4-fold or greater response would not be expected. This response does not seem to be significantly affected by age, sex, IgG level, or IgG subclass value.
authors.affiliation: Division of Allergy-Immunology, Department of Internal Medicine, University of Iowa Hospitals and Clinics, Iowa City, Iowa 52242, USA.
authors.forename: Nathaniel D
authors.initials: ND
authors.lastname: Hare
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Smith
authors.forename: Zuhair K
authors.initials: ZK
authors.lastname: Ballas
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000907:Antibodies, Bacterial / Q000097:blood / Q000276:immunology*; D000917:Antibody Formation / Q000187:drug effects / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D022242:Pneumococcal Vaccines / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology*; D012189:Retrospective Studies; D012737:Sex Factors; D014611:Vaccination
chemical_list: D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; D022242:Pneumococcal Vaccines